2008 C300
Car battery dies randomly. Figured it was bad battery but I saw the car turn on one of the low beams or break lights. Happens completely randomly throughout any time the car is not on. It still happens if I turn the lights to Off or to automatic before shutting the car off.

I brought to a mechanic and there is no way for them to figure out what it could be.

I heard that it could be a relay that needs to be changed so it does not draw from the battery randomly and the car doesn't die. I have had little luck researching what relay it could be and my mechanic says he needs to know which one to go from there.

Has this happened to anyone else? Is there a specific part that could be faulty? Is it the computer itself?

I appreciate any help!!
thank you

 

The headlights are controlled by the SAM (Signal Acquisition Module) which is much more that a simply relay. It sounds like yours is failing and needs to be replaced. Someone with the proper diagnostic equipment (like a Star system) can access the SAM and check for faults. If it is the SAM, inspect the old one for water damage. It's location makes is susceptible to leaks around the windshield area.